Printer hammer assembly



Nov. 12, 1963 J. FRADKIN 3,110,250

PRINTER HAMMER ASSEMBLY Filed Nov. 20, 1961 PRIOR PRESENT DEV'CES INVENTION 2O 4O 6O 80 I00 I2 0 l4 -O I I l l l MILLIONS OF OPERATTONS FIG. 6

TIME OF FLIGHT INVENTOR.

JOSEPH FRADKI N FIG. 5

ATTORNEY United States Patent 3,110,258 PRENTER HAMhiER ASSEBELY Joseph Fradiiin, Plainview, NFL, assignor to Potter instrument Company, Inc., Plainview, N.Y., a corporation of New York Filed Oct. 20, 1% Ser. No. 1%,56tl 2 Claims. ('31. fill-93) This invention, generally, relates to printer hammers and, more particularly, to a printer hammer assembly including a frictionless support for a relatively small displacement.

In the process of printing hard copy at high speeds, printer hammers which strike paper and/ or ribbon usually move through small angles at extremely high speeds. These hammers must be pivoted and controlled accurately since the hammer head must strike the same spot repeatedly upon command.

In the past, journal, ball or roller type bearings have been used to support printer hammers. However, all of these hearings have parts which move relative to one another, and in time, this relative motion of the bearing parts produces wear resulting in dimension changes in the bearing and loss of accurate position control of the pivoting hammer.

Accordingly, it is a principal object of this invention to provide a printer hammer assembly which includes a frictionless support bearing.

Also, it is an object of the invention to provide a support bearing in a printer hammer to achieve an assembly which is substantially free from wear during a relatively long period of high speed operation.

A further object of the invention is to provide a frictionless printer hammer-bearing assembly for movement through a relatively small angle.

A still further object of the invention is to provide a printer hammer-support bearing assembly to permit movement through relatively small angles repeatedly with substantially no Wear.

Another object of the invention is to provide a printer hammer-bearing assembly for permitting relatively small displacement and exhibiting low cost in manufacture.

Still another object of the invention is to provide a printer hammer-bearing assembly permitting small displacement and permitting insulation between the supported members.

Yet another object is to provide a printer hammersupport bearing assembly which permits movement between supported elements and provides also a bias force tending to return the printer hammer to an initial, predetermined relative position.

Briefly, the invention includes a printing hammer with elastomeric means to support the hammer for movement through a small displacement, such assembly being uniquely adapted for use in a high speed printer, for example. An axis defines a relative fixed reference, and a printing hammer is supported on the axis for movement through a small displacement relative to the axis. An elastomeric means is disposed between the axis and the printing hammer to support the hammer for movement pivotally on the axis.

When the elastomeric means is fixedly attached to the axis and printing hammer, the resilient or elastic characteristics of the elastomeric means provides a bias force which urges the hammer to return to its initial, retracted position relative to the fixed axis. However, this characteristic is not particularly advantageous for printer hammer bearings since it is not sufiiciently quick-acting, and therefore, in accordance with the invention, it is necessary to provide a separate hammer-return device, such as a spring for example.

The above and other objects and advantages of the in- Fatentesl Nov. 12, 1963 vention will be more readily apparent from the description which follows taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a high speed printing drum which is typical of the type-supporting element used with an assembly in accordance with the principles of the invention;

FIG. 2 is a partial side view of a printing hammer and bearing assembly in accordance with the invention;

FIG. 3 is an enlarged view of the hammer support in accordance with the principles of the invention;

FIG. 4- is an exploded view of component parts of one hammer bearing;

FIG. 5 is a detailed view of one mount for the printer hammer-hearing assembly of the invention; and

FIG. 6 is a set of curves illustrating the Time of Flight characteristics of the invention as compared with prior devices.

Printing hammer assemblies of the kind to which the present invention relates operate customarily at extremely high speeds, and it is essential too that such operation be in a consistent manner. In other words, each hammer in a high speed printer apparatus should strike a type with substantially the same force and substantially the same way each time during operations that total in the millions.

Each time a printing hammer is struck during high speed operation, stresses of considerable magnitude are developed in the hammer and its supporting pivot. The operating speeds of these printers have been increased a further increment by reducing the mass and size of each printer hammer, the result being that the large stresses are transferred to the hammer pivots.

Due to the large stresses that must be absorbed by the hammer pivots, excessive Wear results, and a substantial decrease in the operating life of conventional pivots is xperienced. Since only a small amount of Wear is sufficient to cause erratic operation, the life of conventionally pivoted printing hammers is short, and frequent replacement has presented an unattractive feature in todays high speed printers.

Referring now to FIG. 1 of the drawings, a high speed printer drum 1 is carried by a shaft 2 for rotation by conventional means, not shown. The surface of the drum it carries rows of type faces 3--4-5 which are provided as raised letters and/ or figures. While this drum 1 is typical of those to be used with the hammers of the present invention, it is not intended to limit the invention to a particular type-supporting member.

in 2 of the drawings, a hammer 7, in a typical assembly in accordance with the present invention, is positioned contiguously with the drum 1 for printing on a paper sheet t; in response to an impact of a hammer head 3. The hammer '7 carries an impact head 8 at one end and the opposite end 9 is located appropriately to be pulled by a magnet core i in response to printing current applied to ends 32 and 13 of a coil 11 from a suitable external source, not shown.

The hammer 7 carries an annular bearing 14 which contains an annulus of elastomeric material is acting as an elastic support bearing between the hammer 7 and a sleeve 16 tted on a center axis pin 17. These parts, that is the bearing parts 14, 15, i6 and 17 are tightly fitted together and, if necessary, are cemented at one or more of the interfaces so that when the hammer is rocked in operation, all of the motion at the bearing consists in deformation of the elastomeric material 15. There is no sliding between parts at the interfaces.

When the center axis pin 17 is held so that it cannot rotate, as will be more fully set forth below, the restoring forces in the elastomeric bearing material will tend to keep the hammer 7 pulled back in its retracted, nonoperating position against an adjustable stop 21 set in a frame 2%). When the electromagnet coil 3.1 is energized, the end 9 of the hammer 7 is pulled toward the core 19, and the hammer head 8 is moved toward drum 1 with an impact to press the printing sheet 6 against a character such as 3, 4 or 5 until the arm of the hammer rests against an adjustable depth-of-penetration stop carried by frame 22. i Y

When the magnetizing current is removed from the coil 11, the hammer 7 is restored to its initial retracted position against the stop 21 due in a small part to the elastic restoring force of the elastomeric material 15. However, it has been found that the hammer construction herein above described in accordance with the present invention is capable of extremely high speed op eration when a biasing spring S is positioned to urge the hammer '7 in its retracted position.

PEG. 3 shows an enlarged view of the hammer bearing assembled in accordance with the present invention. This figure shows the hammer body '7 broken away, the annular bearing 14, the elastomeric material 15, the sleeve 16 and the center pin 17. These parts are all assembled in such a manner that when the pin 17 is firmly held and the hammer body 7 is pivoted with the pin 17 as a center axis, the motion is entirely taken up by deformation of the elastomeric material 15 with no relative movement between the various parts at their boundaries.

In FIG. 4, the essential parts of the hammer bearing are exploded to re'eal their interconnection in accordance with the present invention. This view shows the hammer body 7 (broken away on both sides) with the annular bearing 14 secured to it as by welding, after which the inner bore 18 is machined to precise size and perpendicularity to the body 7. The elastomeric material 15 is bonded to the sleeve 16 which in turn has an accurately determined center hole 19.

if desired, the elastomeric material 2.5 may be formed oversized by a predetermined amount so that when it is pushed into the hole 18 in the annular bearing 14, a tight fit is provided. This iit should be tight enough so that when the hammer is rocked or pivoted, no sliding motion takes place between the bearing 14 and material 15.

To complete the assembly, the axis pin 17, which is slightly larger in diameter than the hole 19, is pressfitted into the hole 19, whereby the whole assembly forms an'integral unit with relative motion between the pin 17 and the hammer 7 being provided solely by deformation of the elastomeric material 315.

FIG. 5 is an assembled view of the components shown in PEG. 4 mounted in an operating assembly, wherein the center pin 17 is carried by stationary frame supports 24 and 25 and is held stationary by suitable means, such as a setscrew 26. Thus, when the hammer arm '7 is rocked or pivoted, as in the printing operation, the relative motion between the arm 7 and the pin 17 (and frame 25) is provided by the deformation of the elastomeric bearing, as described above.

FiG. 6 is a set of curves illustrating the characteristics of the hammer-bearing assembly of the present invention in comparison with hammer-bearings of prior types. The Timeof-Flight is shown on the vertical scale while Millions-of-Operations is used as the horizontal scale.

Typical of the operation of previously available harnmer-bearing assemblies, the curve showing large variations in Time-of-Flight is labeled Prior Devices. These variations are not only large but do not follow a regular pattern.

The Time-of-l light for the assembly in accordance with the present invention shows very much smaller deviations from a constant value, as indicated by the curve labeled Present invention. These curves are typical of the reat improvement provided by bearings constructed in accordance with the present invention.

The use of elastomeric material as a support for a printing hammer was ruled out when first considered, bec use it was thought that such a support would not permit the maintenance of the strict alignment required for this type of hammer. In addition, it was thought that the frequent, high speed deformation of an elastomeric material in this environment would develop overheating and result in early molecular breakdown.

However, actual tests have shown that quite accurate hammer alignment can be obtained and maintained throughout long operations of a printer apparatus. Moreover, no overheating was experienced in tests running into millions of operating cycles.

Other disadvantages that had been expected include a large damping action due to an elastomeric support being still as compared, for example, with a ball bearing support. Such damping would take the snap (quick response) out of the hammer and increase the striking time.

However, it was found that the striking time was not affected by the elastomeric material, and actually, this type of support was ellective in decoupling mechanical forces between adjacent hammers, thus filtering out hightransient shocks. Also due to the elastomeric support for printer hammers, the frame (identified in FIG. 5 by the numerals 2.4 and 25) may be structurally weaker providing a saving in material.

A distinctive advantage which was discovered to be available in an assembly of the invention is the sharper and more consistent impressions that are made by the print type on the paper. It is believed that this advantage is realized because of the slight rocking action which is developed in the hammer (similar to the action obtained by rocking a hand stamp before removing it from the paper).

In addition, the elastomeric member separates the shaft rom the hammer both electrically and electrolytically, as will be understood readily.

While there have been shown and described and pointed out the fundamental novel features of the invention as applied to a preferred embodiment, it will be understood that various omissions and substitutions and changes in the form and details of the device illustrated and in its operation may be made by those skilled in the art, without departing from the spirit of the invention. It is the intention, therefore, to be limited only as indicated by the scope of the following claims.

What is claimed is:

1. In a high speed printer adapted for repeated use at high speeds having a continuously moving type-supporting element, the combination of, at least one pivotably operable printing hammer, electromagnet means positioned contiguously with said printing hammer to actuate said hammer to a printing impact position from a retracted non-printing position, a rigid axis means to locate said hammer relative to said type-supporting element, and an elastomeric bearing means in substantially slip-firee relation between both said hammer and said axis means to be distortable permitting said hammer to be pivoted about said axis means through a relatively small angle for impact with type carried by said type-supporting element.

2. in a high speed printer as set forth in claim 1 including frame means to support said rigid axis means for a predetermined number of said printing hammers.

References Cited in the file of this patent UNITED STATES PATENTS 1,025,20 Paulson May 7, 1912 2,805,629 Rosen et al Sept. 10, 1957 3,003,416 Gro-bman Oct. 10, 1961 

1. IN A HIGH SPEED PRINTER ADAPTED FOR REPEATED USE AT HIGH SPEEDS HAVING A CONTINUOUSLY MOVING TYPE-SUPPORTING ELEMENT, THE COMBINATION OF, AT LEAST ONE PIVOTABLY OPERABLE PRINTING HAMMER, ELECTROMAGNET MEANS POSITIONED CONTIGUOUSLY WITH SAID PRINTING HAMMER TO ACTUATE SAID HAMMER TO A PRINTING IMPACT POSITION FROM A RETRACTED NON-PRINTING POSITION, A RIGID AXIS MEANS TO LOCATE SAID HAMMER RELATIVE TO SAID TYPE-SUPPORTING ELEMENT, AND AN ELASTOMERIC BEARING MEANS IN SUBSTANTIALLY SLIP-FREE RELATION BETWEEN BOTH SAID HAMMER AND SAID AXIS MEANS TO BE DISTORTABLE PERMITTING SAID HAMMER TO BE PIVOTED ABOUT SAID AXIS MEANS THROUGH A RELATIVELY SMALL ANGLE FOR IMPACT WITH TYPE CARRIED BY SAID TYPE-SUPPORTING ELEMENT. 